duel adau1701 different sample rates?

On the ADAU1701, the serial port rate should be running at the same rate as the SigmaDSP core. In order to connect two devices running at different sampling rates, you would need to use a sample rate converter (SRC) between the two serial ports. The AD1895 is a good choice for a stand-alone stereo SRC. The ADAU1442 and ADAU1445 SigmaDSPs also have integrated SRCs.